Redundant Ethernet networking has traditionally been limited, by its absolute requirement for loop avoidance, to the use of a simple spanning tree, which results in the blocking of all except one path between endpoints. Recent application of Link-state routing to Ethernet (e.g., in SPB and E-VPN) have allowed this spanning tree requirement, and its undesirable blocking consequences, to be mitigated, but only within a single network domain controlled by a single protocol. For example, SPB Media Access Control (MAC) bridging (SPBM), defined in IEEE 802.1aq-2012, the contents of which are incorporated by reference herein, describes the IEEE link-state routing solution for Ethernet MAC-in-MAC, with all paths within an SPBM domain unblocked. SPBM is a native Ethernet link-state technology. E-VPN is an emerging IETF technology for Ethernet emulation over Multiprotocol Label Switching (MPLS). An E-VPN includes Customer Edges (CEs) that are connected to Provider Edges (PEs) that form the edge of the MPLS infrastructure. A CE may be a host, a router or a switch. The PEs, also known as MPLS edge switches (MES) in E-VPN documentation, provide virtual Layer 2 bridged connectivity between the CEs. There may be multiple E-VPNs in a provider's network.
EVPN is the likely successor to VPLS for delivery of Carrier Ethernet services due to significant improvements over VPLS. For example, EVPN is described inter alia in various Layer 2 Virtual Private Network Working Group drafts such as draft-ietf-12vpn-evpn-01 entitled “BGP MPLS Based Ethernet VPN” (July, 2012), draft-ietf-12vpn-pbb-evpn-03 entitled “PBB-EVPN” (June, 2012), and draft-allan-12vpn-spbm-evpn-01 entitled “802.1aq and 802.1Qbp Support over EVPN” (July 2012), the contents of each are incorporated by reference herein. The document draft-ietf-12vpn-evpn-01 describes a technique emerging from the IETF to carry Ethernet over MPLS and also describes inter alia how to dual-home a single MAC-in-MAC CE (running IEEE Link Aggregation Group (LAG)) with multiple E-VPN PEs whilst achieving active-active operation. The draft draft-ietf-12vpn-pbb-even-03 describes how the scaling problems of E-VPN can be mitigated by “front-ending” that technology by a MAC-in-MAC Ethernet technology, such as Provider Backbone Bridging (PBB) or SPBM. However, there is no specification of active-active operation with multiple redundant CEs. For network-network interworking, draft-ietf-12vpn-pbb-evpn-03 and draft-allan-12vpn-spbm-evpn-01 both describe variations of a technique in which a MES forming one of a number of gateways to a MAC-in-MAC island may be elected as the single Designated Forwarder for a subset of the Ethernet services, which can be used to spread services between gateways. This has the disadvantages that load spreading is suboptimal with small numbers of large services, and that failure of a gateway node requires reassignment and re-announcement of service-to-gateway bindings which will severely impact restoration times.
A technique has not yet been identified for the achievement of fully link- and node-redundant interworking without service awareness between SPBM and E-VPN whilst maintaining active-active operation. This is an important aspect for Ethernet service delivery. In particular, on the interface between a customer or service provider edge SPBM network and a service provider core E-VPN network, there is a need for redundant connectivity (for resiliency), and a strong desire for “active-active” operation with excellent load sharing (so that no bandwidth is stranded).